The goal of this project is to understand, predict and control the conformation of nucleic acids. The conformation in turn controls the biological function of the nucleic acid. The main emphasis will be on the effect of mutagens on DNA structure and DNA replication. Oligodeoxynucleotides of specific base sequence will be studied in the presence of covalently and non-covalently bound mutagens. The effect of the mutagen on the stability of base pairs and base mismatches will be measured. The structures of the DNA-mutagen complexes will be determined using circular dichroism, temperature-jump kinetics and other physical properties. The molecular mechanism of mutagenesis will be studied by incorporating chemically modified oligodeoxynucleotides into DNA and determining the base sequence of the replicated oligomer.